While, in the prior art, triethylene diamine was prepared from aminoethyl piperazine as the starting material, a method has been developed in recent years to give a high yield from hydroxyethyl piperazine as the starting material using a calcium phosphate-based catalyst (Japanese Patent Kokai 58-17839).
These starting compounds, however, are expensive with low availability so that the above described methods are not suitable for practice.
On the other hand, Japanese Patent Kokai 51-141895 discloses a method for the preparation of triethylene diamine by bringing diethanol amine as the starting material into contact with an alumina catalyst, silica-alumina catalyst or silica-alumina catalyst substituted by metal ions. This method, however, is a two-step process in which an intermediate is prepared in the course thereof and subsequently triethylene diamine is prepared and the yield is low in addition to the troublesomeness of the working procedure.
The present invention has an object to develop a method for the preparation of triethylene diamines in a simple procedure and still in a high yield by use of various kinds of readily available starting compounds overcoming the above described defects in the prior art technology.